Asthma is the most common chronic childhood disease and the most frequent reason for hospitalization of children. It is also the most common chronic respiratory disorder in adults. It results in over 1.7 million emergency department visits and about 450,000 hospitalizations annually in the U.S. alone. The National Institutes of Health (NIH) expert guidelines recommend the measurement of Pulsus Paradoxus (the variation in systolic blood pressure that occurs with inspiration and expiration) as a clinical standard for determination of acute asthma exacerbation severity and to help guide appropriate treatment and hospitalization decisions for these patients. Currently, however, there are no invasive or noninvasive monitors for the automated measurement of Pulsus Paradoxus. Worse still the only clinically-available noninvasive technique is performed using a stethoscope and a blood pressure cuff and is so time consuming and difficult to perform in a clinical environment that compliance with this NIH recommendation is estimated at less than 1%. Given the well-recognized clinical value of Pulsus Paradoxus, and the enormous financial burden of acute asthma attacks on the healthcare system, it is clear that an automated, easy-to-use, noninvasive monitor for Pulsus Paradoxus would improve patient care and reduce unnecessary hospital re- admissions, increase compliance with NIH recommendations, and decrease healthcare costs associated with acute asthma. This SBIR Grant proposal is designed to determine whether Pulsus Paradoxus information is contained in the raw pulse oximetry data, and whether these data can be extracted and processed to provide an accurate, noninvasive, real-time measurement of Pulsus Paradoxus. What sets this grant up for success is the combination of expertise provide by having two principal investigators. One is a clinical expert in asthma diagnosis and treatment, including prior work studying current methodologies and research concepts for the measurement and use of Pulsus Paradoxus, and the other has over 30 years in the field of pulse oximetry technology and product development. Once this proof of concept study is successfully completed, Phase II work would include integrating this measurement into an existing pulse oximeter to provide easy-to-use, real-time measurement of this crucial parameter and to demonstrate that this capability could increase compliance with NIH guidelines from the current <1% to over 80% in the clinical environment.